I'd hardly ever use a 7th in an Irish session. Oh I might use the occasional A7, but only because I was getting cranmp playing an A and the fingers needed a change. And I've noticed that when I write the chords for song I've written, I hardly ever use a major 7th. I just don't tend to like the sound. (Minor 7th - now I like them - God knows why. It's a personal quirk.)